A FASTENER FOR A BAG

Abstract: A plastic clip (30) is located at each end of a plastic zipper (11) of a thermoplastic bag (B) and fused with the ends of the profile elements (16, 17) of the zipper (11) into a single mass by melting the clip (30) to the zipper material.

Description: A Fastener for a Bag The present invention relates to a fastener for a bag. More particularly the invention relates to improvements in plastic reclosable fasteners with sliders for opening and closing the plastic bags and the like. Plastic reclosable fasteners with sliders (also known as zippers) are well known in the art. Such fasteners have profiles which include a pair of male and female fastener elements in the form of reclosable interlocking rib and groove profile elements for cooperation with a slider for opening and closing the rib and groove elements. In the manufacture of thermoplastic film bags, a pair of these male and female plastic profile elements extend along the mouth of the bags and these male and female elements are adapted to be secured in any suitable manner to the flexible walls of the thermoplastic film bags. These profile elements may be integral marginal portions of such walls or they may be extruded separately and thereafter attached by a fin to the walls along the mouth of the bag. Various arrangements have been utilized previously to prevent the slider from sliding off the ends of the zipper. In one of the more conventional arrangements the slider included a separator finger that extends down between the integral locking rib and groove elements as the slider is moved from one edge of the bag to the other edge of the bag. When the bag is opened, the only thing to stop the slider was the side seam at the edge of the bag when the slider finger comes into contact with it. This prior art is described in US-A-3790992, which discloses an arrangement wherein the heat seals that join the rib and groove elements are wider at one edge than the second edge of the bag and the wider seal is of a width at least equal to the length of the slider from its closing end of the finger, so that the slider will remain fully on the bag at the end of its travel when opening the bag. The patent points out that these seal areas provide stops for the slider. Another arrangement for providing stops at the end of the zipper is disclosed in US-A-3259951, which discloses that the opposite ends of the interlocking or mating strips are permanently joined or sealed to each other at the ends with the stop members sealed between the opposite ends of these members to stop the longitudinal movement of the slider therealong. US-A-5088971 and US-A-5131121 disclose end stops at the opposite ends of the reclosable fastener where the end stops are formed from the material at the opposite ends of the reclosable fastener and protrude transversely from the fastener a distance adequate to engage the slider and prevent movement of the slider past the respective ends of the bag. With this arrangement the size of the end stops is limited by the amount of material in the ends of the fastener. Another prior art arrangement is shown in US-A-5161286 which discloses that the end clamp members are located at the opposite ends of the reclosable fastener and the end clamp members are connected together by a flexible strap which extends over the top of the zipper and the rivet extends through the clamp members and the sidewalls of the bag beneath the profile elements of the zipper to secure the clamp members to the bag. It would be desirable to provide the plastic bags wherein the fastener is terminated by end clips and the fasterner and end clips are fused into a single mass to create a stronger seal - because it is not limited to the cross sectional area of the profile elements and does not rely on a rivet for the strength of the seal. The present invention provides a strong and leakproof joint and is an improvement on the end stops for plastic reclosable fastener disclosed in US-A-5088591, US-A-5131121 and in US-A- 5161286 thereto. It is an object of the present invention to provide a bag having a plastic fastener with improved means for attaching the ends of the two zipper elements together so they are strong and leakproof and capable of retaining a slider on the fastener. According to one aspect of the present invention there is provided a reclosable fastener for a bag, said fastener being adapted to extend along the mouth of the bag, and comprising a pair of flexible plastic strips adapted to be secured to the facing side walls of the bag and having reclosable interlocking male and female profile elements on the respective strips, wherein the fastener further comprises end clip means located at the opposite ends thereof, and each of said end clip means comprises a plastic member extending over the top of said reclosable strips and fused with the ends of the male and female profile elements into a single mass so they are leakproof and integral with the plastic member, and each said plastic member and said male and female profile elements is made of compatible plastic materials so that they can be fused together. Advantageously the fastener further comprises a slider straddling the strips for opening and closing the fastener. In one embodiment the plastic members and said male and female profile elements are all made of polyethylene. In another embodiment said male and female profile elements are made of polyethylene and said plastic members are made of an ethylene-propylene copolymer. Preferably, said end clip means comprises a plastic strap member, more preferably a substantially U-shaped plastic member. Desirably said end clip means after fusion to the male and female profile elements projects outwardly therefrom. According to another aspect of the invention there is provided a method of making a leakproof reclosable fastener comprising the steps of positioning end clip means at the opposite ends of male and female profile elements of the reclosable fastener, each of the end clip means comprising a plastic member extending over the top of the male and female profile elements, each of said plastic members and said male and female profile elements being made of compatible plastic materials so they can be fused together, and fusing the plastic member with the ends of the male and female profile elements into a single mass so they are leakproof and integral with each other. In one embodiment the end clip means and the ends of the male and female profile elements are fused into a single mass by melting the end clip means to the male and female profile elements by the application of heat energy. In another embodiment the end clip means and the ends of the male and female profile elements are fused into a single mass by melting the end clip means to the male and female profile elements by the application of ultrasonic energy. Preferably said end clip means is plastic strap member folded over the top of the male and female profile elements. The fastener according to the invention is advantageously provided along the mouth of a thermoplastic bag. Reference is made to the accompanying drawings, in which: Fig. 1 is an elevational view of the series of thermoplastic bags manufactured in accordance with the present invention. Fig. 2 is a perspective view of plastic end clips fused to the plastic fastener material. Fig. 3 is a cross-sectional view taken along the lines 3-3 in Fig.2 showing the end clip extending over the top of the reclosable fastener and fused with the ends of the male and female profile elements into a single mass. Referring to Fig.l there is illustrated a series of thermoplastic bags B each having a plastic slider 10 and a profiled plastic reclosable fastener or zipper 11 with end termination clips 30. The slider 10 and zipper 11 are particularly suited for thermoplastic bags and the like. While various types of sliders and zippers maybe used with the new end termination clips 30, the slider 10 has been illustrated as of the type disclosed in US-A-5067208 and the zipper 11 has been illustrated as of the type disclosed and claimed in US-A- 5007143. As shown in Fig. 1 the slider 10 is assembled on the zipper 11 at the top edge or mouth of the thermoplastic bag B. The bag B may be made of any suitable thermoplastic film such for example as polyethylene or polypropylene or equivalent material. The zipper 11 preferably is made from the same plastic material as the bag B. The bag B is formed by a pair of flexible plastic sheets 12 and 13 joined at the bottom and having a top edge, with a pair of flexible plastic strips or fins 14 and 15 having separable plastic means extending along the length thereof comprising reclosable interlocking male and female profile elements in the form of rib and groove elements 16 and 17 on the respective strips to form the zipper 11. The strips 14 or 15 may be extruded separately and attached to the respective sides of the bag mouth or the strips 14 and 15 may be extruded integrally with the sides of the bag mouth. The strips 14 and 15 include profiled tracks 18 and 19 extending along the length thereof parallel to the rib and groove elements 16 and 17. The rib and groove elements, 16, 17 may have various complementary cross-sectional shapes. However, the shapes of the elements disclosed herein are such that they are closed by pressing the bottom of the elements together first and then rolling the elements to a closed position toward the top thereof. The cross-sectional shapes of the interlocking male and female elements having the rib and groove profile 16 and 17 and are dislosed in US-A-5007143. The slider 10 straddles the zipper 11 at the top of the bag B and is adapted for opening or closing the reclosable fastener elements 16 and 17 of the zipper 11. The slider 10 moves along the zipper 11 from one end to the other and includes a separator finger (not shown) which cooperates with the tracks 18 and 19 (see Fig. 2) to open and close the zipper 11. The slider 10 may be molded from any suitable plastic such for example as nylon, polypropylene, polystyrene, Delrin, or ABS. Referring to Figs. 1 and 2 it will be seen that the opposite ends of the zipper 11 are provided with end clips 30. Each of the end clips 30 is identical and each end clip 30 comprises a strap member which wraps over the top of the zipper 11 in substantially U-shaped form. As shown in Fig. 2 there is illustrated a pair of typical end clips 30 that form the right end of one bag and the left end of the next bag. For ease in manufacture of the bags, the end clips 30 can be formed as a single unit, with the two clips attached by a tie bar made of the same material, or they may be separate clips. Each clip 30 is wrapped around the profile elements at the ends of the bag and then sealed along with the profile ends to form a fused mass. The clips 30 may be held by an insertion device while they are sealed to the zipper 11, or the clips may be inserted so that they hold themselves in place while the clips are subsequently heated and sealed. To hold the clips 30 in place by themselves, the clips may be provided with an integral pin that penetrates the zipper fin. The sealing operation may be performed by a pair of heated jaws or by ultrasonic energy. The sealing energy must be adequate to fuse the plastic strap member 30 with the ends of the male and female profile elements into a single mass so that they are leakproof and integral with the strap member. It is necessary that the clip 30 and zipper 11 be made of compatible materials that can be fused together. For example, both the clip 30 and the zipper 11 can be made of polyethylene, or the zipper 11 can be made of polyethylene while the clip 30 is an ethylene-propylene copolymer. It will be noted that the end clips 30 after being fused to the zipper 11 extend outwardly from the zipper and thus are engageable with the slider 10 for preventing the slider from moving past the ends of the reclosable fastener or zipper 11. Also, by providing additional thermoplastic material at the ends of the zipper elements, this ensures that when the clip and zipper material are melted and fused together, the joint formed therebetween will be strong and leakproof. The end stops formed by the end clips 30 in the present invention represent an improvement over the end stops disclosed in US-A-5088971 and US- A-5131121. In those patents the end stops were formed solely by fusing the ends of the profile elements in the zipper and thus the amount of material available for forming the end stops and sealing the profile elements of the zipper was limited to the material in the zipper elements. Such a limitation is eliminated in the present invention by the use of the additional end clips 30. The method of installing the end clips 30 disclosed herein also eliminates the need for a pre-seal on the plastic strips 14 and 15 at the side seal locations to reduce the material thickness before installing the end clips 30 as described in the aforesaid US-A-5161286. The end clips 30 in the present invention eliminate the punching of the hole in the bag walls and zipper fins to receive the rivet disclosed in US-A-5161286 thereby eliminating a source for leakage. After the end clips 30 have been sealed to the ends of the bags, a side seal is formed across the thermoplastic sheets between the bags and the bags are severed from each other as shown in Fig. 1. While a preferred embodiment of the invention has been described and illustrated, it is to be understood that further modification thereof may be made within the scope of the appended claims.

Claims: Claims ; 1. A reclosable fastener for a bag, said fastener being adapted to extend along the mouth of the bag, and comprising a pair of flexible plastic strips adapted to be secured to the facing side walls of the bag and having reclosable interlocking male and female profile elements on the respective strips, wherein the fastener further comprises end clip means located at the opposite ends thereof, and each of said end clip means comprises a plastic member extending over the top of said reclosable strips and fused with the ends of the male and female profile elements into a single mass so they are leakproof and integral with the plastic member, and each said plastic member and said male and female profile elements is made of compatible plastic materials so that they can be fused together. 2. A fastener according to claim 1, wherein the fastener further comprises a slider straddling the strips for opening or closing the fastener. 3. A fastener according to claim 1, wherein said plastic members and said male and female profile elements are all made of polyethylene. 4. A fastener according to claim 1, wherein said male and female profile elements are made of polyethylene and said plastic members are made of an ethylene-propylene copolymer. 5. A fastener according to claim 1, wherein said end clip means comprises a plastic strap member. 6. A fastener according to claim 1, wherein said end clip means comprises a substantially U-shaped plastic member. 7. A fastener according to claim 1, wherein said end clip means after fusion to the male and female profile elements projects outwardly therefrom. 8. A thermoplastic bag comprising a body and a mouth, which provides an opening into the body, and a fastener according to claim 1 disposed along said mouth on opposing sides of the bag. 9. A method of making a leakproof reclosable fastener comprising the steps of positioning end clip means at the opposite ends of male and female profile elements of the reclosable fastener, each of the end clip means comprising a plastic member extending over the top of the male and female profile elements, each of said plastic members and said male and female profile elements being made of compatible plastic materials so they can be fused together, and fusing the plastic member with the ends of the male and female profile elements into a single mass so they are leakproof and integral with each other. 10. A method according to claim 9, wherein the end clip means and the ends of the male and female profile elements are fused into a single mass by melting the end clip means to the male and female profile elements by the application of heat energy. 11. A method according to claim 9, wherein the end clip means and the ends of the male and female profile elements are fused into a single mass by melting the end clip means to the male and female profile elements by the application of ultrasonic energy. 12. A method according to claim 9, wherein said end clip means is plastic strap member folded over the top of the male and female profile elements.

Inventors: HERRINGTON FOX JOHN, HERRINGTON, FOX, JOHN
Applicants: MOBIL OIL CORP, MOBIL OIL CORPORATION
Application year: 1994
Main classification: A44B19
IPC codes: A44B9, A44B19, B65D33